Electrical contact plug



March 3, 1936. KLEINMANN r A 2,032,847

ELECTRICAL CONTACT PLUG I Fild Jan. 8,' 1930 5/ M wmw Patented Mar. 3, 1936' T TED STATES PATENT OFFICE 2,032,841

ELECTRICAL CONTACTPLUG' and Alfred Mend,

Germany Kleinmann Berlin-Lichtenberg,

Application January 8, 1930. Serial No. 419,241 In Germany January 31, 1929 11 Claims. (01. 173-361) This invention relates to electrical contact plugs such as are commonly used in electron discharge tubes. Such plugs-are'now generally made in whatis called banana shape, that is they are substantially cylindrical but are bulged outwards about their centres so as to make resilient contact with the sockets into which they are inserted. Sometimes the plugs are taken and bored from solid rods, the tops being left closed, but

generally they'are hollow throughout and openat the top. In the manufacture of electron discharge tubes these plugsare moulded into position in bases of bakelite or the like so that special devices have to be inserted in the tops of the plugs to close them, or the bakelite would enter the plugs and completely fill them. The bakelite moulding is bored through so as to provide a passage for the leading-in wires of the various electrodes of the electron discharge tube or the go like.

avoid the necessity of inserting special devices during the moulding operation. Another object of the invention is to provide a contact plug well able to withstand lateral stresses. Yet another 26 object of. the invention is to devise a novel plug capable of being manufactured cheaply by mass production.

According to the present invention, an electrical contact plug is made from'a single piece of 80 stamped sheet metal having a closed top, so that when it is moulded into position in the base of a valve or the like, none of the moulding materials can enter the .plug. In carrying the invention into eifect it is preferred to stamp the top edge 85' of each section of flat sheet metal in zig-zag form,

the section being then bent and shaped into cylindrical form and the zig-zags being bent inwards so as to close the top. When it is desired to make banana plugs, slits may be cut longi-- 40 tudinally in the flat sheet metal, but not extending to either end, and after the metal has been rolled into cylindrical formthe cylinder may be subjected to an axial pressing action so that its centre part bulges outwards. These slits are 45 preferably formed by dividing the metal without any material being actually removed. By this Yet a further' feature of the invention con-- sists in forming the lower ends of the sheet metal sections with zig-zags, and in cutting oil the tips 55 of the zig-zags when the metal is rolled into cylin- One object of the present invention is to drical form. These zig-zags can then be turned inwards, but owing to the fact that their tips have been removed a small hole will be left at the bottom of the plug which allows of the introduction of a small piece of solder to fix the leading-in wire close to the bottom of the plug on the inside.

According to-yet a further feature of the invention, in order to increase the resistance of the plug to lateral stresses the top of the plug is made in the shape of a frustrum of a cone having its 10 narrow end adJacent to the closed end of the plug. This frustrum may very conveniently run between two transverse ridges which may 1 be embossed during the process of manufacture.

In order that the invention may be clearly understood and readily carried into efl'ect, several Figure 6 shows the finished banana plug, and 36 Figure 7 shows another form of stamping.

Figure 8 shows another modified form of plug, and

Figure 9 shows yet a further modified form of PluB- Referring first to Figure 1, an electron discharge tube I is illustrated with a moulded base 2 containing contact plugs 8. Each of these plugs is formed from a stamping [having at the upper end zig-zags I and at the lower end zig 40 'zags 8, the tips of which are cut off. At the same time as the sheet metal is stamped into the shape showninFigure 2,aridge'lis embossedupon it. .I'he sheet metal stamping l is then rolled into the cylindrical form shown in Figure 3. It is found in practicethat the bore of the cylinder is too small to allow of a former being employed,

and the rolling of .the metal is preferably effected by bending it twice at right angles so as to form a channel section and then pressing the channel section into a cylinder. The zig-zag ends I and 6 are then closed in by means of cup-like dies, and at the same time a second ridge or an.-' nul-ar projection I is formed. This is effected by- .hflding the lower part of the plug tightly, and

pressing the upper part towards it axially so that some of the metal is compelled to bulge outwards to form the ridge 8. These ridges 1 and 8 are provided in order that the finished plugs I may be easily located within the moulding 2 of an electron discharge tube, and may be prevented from moving axially.v A series of interruptions 9 may be formed around one or both ridges I and 8 so as to prevent the plugs rotatingwithin the moulding 2.

The .lower zig-zag projections 6 are closed in, but since their tipsare cut away a small hole is left in the bottom of the plug through which the leading-in wires can be soldered to the inside of the plug.

It is found in practice that it is best if the closed in-top oi the plug is pointed and has curved sides as shown in Figure 4, and that the angle indicated by it! should lie between 80 and -l20. In other words, the angle of the pointed arch of the closed head or top is determined approximately by taking both the tangents of the curved sides, and the reference numeral Ill merely designates the ordinary circular line running between the two tangents and showing the angle in question.

In the construction shown in Figures and-6, the stamping 4 is made with one straight side and with one side slightly bulged outwards as shown at H the bulge being greatly exaggerated in the figure. Two slits I! are cut in the sheet metal during the stamping operation, these slits being purely division of the metal and no actual material being removed; The stamping 4 is then bent and shaped into cylindrical form as before, and at the same time that the top and-bottom are closed in, the whole plug is compressed axially so that it assumes the banana shape shown in Figure 6. Since no metal is cut away in forming the slits l2, the openings produced when the plug is forced into banana shape are not so wide that they will allow the leading-in wires of an electron discharge tube to pass through. The opening shown at l3 in Figure 6, which is produced at the seam of the cylinder, is equally of suitably narrow width on account of the bulging out of the part II during the stamping operation, whereas if both sides of the stamping were made straight the opening at the seam would be too wide after the axial compression.

In the stamping shown in Figure 'L'in addition to the projection I two rectangular portions l4 are embossed on the stamping in such awayas to form flats on the finished cylinder. These flats assist to prevent rotation o! the plug dur-'- ing and after the moulding operation. In the construction shown in Figure 8, the upper part of the plug between the ridges I and 8 is made in the shape of a frustrum ll of a cdne instead of'being cylindrical. The construction is such that the ridge I projects outwards from the plug only on its'lower side but on its upper side runs straight into the conical surface. By means of this arrangement the upper part of the plug frustrum l5.

With the novel plug no bakelite or other mould-- I ing powder can-enter the plug during the.op-

eration of moulding the-base, with the result that it is only necessary to bore through the moulding above the plugs and then through the pointed ends oi. the plugs in order tointroduce the leading-in wires into the plugs.

It is to be understood that the claims are not limited to the constructions shown in the drawing since clearly modifications may be made and, therefore, the claims are intended to be construed to cover all such modifications as their language will allow in the light of the prior art.

From the foregoing description, it is apparent that where reference is made to theclosed top of the plug, it means that portion of the plug which is imbedded in the molded base of electron discharge tubes and the like, or it may be more exact to refer to the so-called top end as the "inner end of the plug, for the reason that the opposite end is the outer end when it is mounted for operation in connection with such a discharge tube. Therefore,'in the claims the terms top and inner as referring to the ends of the plug may be regarded as alternative expressions or synonymous.

We claim:

1. An electrical contact plug comprising a single piece of sheet metal formed with at least one V longitudinal slit terminating short of each end of the piece, the portions of said piece on either 'side ofsaid slit being longitudinally convexed,

-be inserted in a socket.

3. An electrical contact plug comprising a single piece of sheet metal shaped into substantially cylindrical form and having a pointed closed inner end, the outer end thereof being adapted to be inserted in a socket, the said inner end having curved sides.

4. An electrical contact plug comprising a single piece of sheet metal shaped into substantially cylindrical form and having a closed conical inner end adapted to be imbedded in a tube base the sides of which when seen in side view subtend an angle lying between 80 and 120'. p a

5. An electrical contact plug comprising a single piece of sheet metal shaped into substantially cylindrical form, having two transverse projecting.

ridges and a closed conical inner end of anchorage in a tube base.

6. An electrical contact plug comprising a single piece of sheet metal shaped so as to present a substantially cylindrical portion, a closed inner end adapted to be anchored in a tube base and having an outer end adapted to be inserted in a socket, the said plug having a frusto-conical portion with its narrow end adjacent said closed inner end, said frusto-conical portion joining said closed inner end and saidcylindrical portion.

7. An electrical contact plug comprising a single piece of sheet metal and shaped so as to present a closed inner end adapted to be anchored in a tube base and having an outer end adapted to enter a socket, a substantially cylindrical portion, two transverse projecting ridges, one of said ridges running into said cylindrical portion and the other 01' said ridges running into said inner end, and a conical portion connecting together said ridges. i

8. An electrical contact plug comprising a single piece of sheet metal shaped into substantially cylindrical form and adapted to be inserted in a I socket at one end and having the other end conical in shape and completely closed for imbedment in a plastic base. I

9. An electrical contact plug comprising a single piece of sheet metal shaped into substantially cylindrical form, the metal at one end of the cylinder being in the form of a plurality of converging portions bent inwards. to bring their adjacent edges into contact to close the end, the

opposite end of the cylinder being adapted to be inserted in a socket. 1

ao'sasm a portions, which portions are bent inwardly with their adjacent edges in contact to close said end, the opposite end of the cylinder being adapted to be inserted in a socket.

11. A bulged electrical contact plug comprising a single piece 0t sheet metal shaped into substantially cylindrical form with opposite edges contiguous, one of these edges being curved outwards so that the contiguity of said edges is maintained substantially uniform in spite of the bulge, an end of said plug being adapted for insertion in a'socket.

ERNST KLEINMANN. ALFRED MENDEL. 

